1. Field of the Invention
In at least one embodiment, the present invention relates to an ambient cured or bake cured sol-gel surface coating that imparts corrosion resistance. In other embodiments, the present invention relates to an ambient curable or bake curable sol-gel coating composition and process for making and using the sol-gel coating composition.
2. Background Art
Sol-gel coatings have been used as conversion coatings for aluminum and other metal substrates such as ferrous and zinc substrates. One particular use of sol-gel coatings has been in the aerospace industry. For instance, sol-gel coatings have been applied to substrates particular to that industry, such as aluminum and titanium alloys, as an adhesion promoter between the underlying substrate and a paint primer, such as an epoxy primer. In addition to being an adhesion promoter, sol-gel coatings can provide good corrosion resistance, particularly on aluminum substrates, when the coating is baked.
Typical sol-gel bake systems are 100° Celsius to 250° Celsius. However, when the sol-gel coating is used on aircrafts, typical sol-gel coatings are not particularly suitable since it is not considered advantageous to expose aircraft substrates to temperatures necessary to achieve baking. The same sol-gel coatings that have good corrosion resistance at the high bake temperatures tend not to perform well when cured in ambient conditions, such as at room temperature, which is the preferred temperature for curing a composition used on the exterior of an aircraft.
Accordingly, it would be advantageous to provide a sol-gel coating that can have favorable corrosion resistance when cured at temperatures less than 100° Celsius and, preferably around room temperature. Moreover, it would also be desirable if such a coating had good corrosion resistance performance at elevated cured temperatures.